Journal of
MEDICINAL AND PHARMACEUTICAL CHEMISTRY Volume 5 , Number 2
0 Copyright 2068 by the American Chcmzcal 9ociety
March 21, 1962
Chemistry and Pharmacology of Monoamine Oxidase Inhibitors : Hydrazine Derivatives F L O Y D E. ~ D E R S O X , DANIELKAMINSKY,~ B E R N A R D DUBNICK, SYLVESTER R. KLUTCHKO, WIACZESLAW A. CETENKO, JONAS GYLYS, .4ND JOHN A. HART
Warnet -Lurribert Reseurch Institute, Aforris Plains, A'. J.
Received October 28, 1961 The preparations and some pharmacological properties of 70 aralkyl hydrazincs arid acylated hydrazines are described. From the data obtained attempts were made to correlate activity with structure. Several highly efficient monoamine oxidase inhibitors were uncovered and presently are undergoing additional laboratory and clinical tests.
During the early clinical testiiig of iproniazid as an antituberculous ngeiit in 1951, the development of euphoria in patients was noted among the side effects of the drug.2 I n 19.52, Zeller and co-workers found that iproniazid is an inhibitor of monoamine oxidase (MAO) in t'ico3 and in vitro4 and suggested the potential antidepressant utility of such a compound which could result from potentiation of amines whose metabolism is normally catalyzed by this enzyme (MAO) in the central nervous system. This possibility was dramatized by Brodie and his associates5and in our laboratory6 with the demonstra(1) T o whom all inquiries regarding this paper should be addressed. (2) This experience is recalled by D. M. Bosworth, Ann. N . Y . Acad. Sei., 80, 809 (1959). (3) E. 4. Zeller and J. Barsky. Proc. Soc. E x p . B i d . 'Wed., 81, 459 (1952). (4) E. A. Zeller, J. Barsky, J. R. Fouts, W.F. Kirchheimer, and L. S. Van Orden. Ezperientia. 8 , 349 (1952). ( 5 ) B. B. Brodie, A. Pletsoher, and P. 4 . Shore, J. Pharmacal. Ezptl. Therap., 116, 9 (1956). (6) 31. Chessin, B. Dubnick, E. R. Kramer, and C . C . Scott, Federation Proc., 16, 409 (1956).
221
tion that rabbits aiid mice pretreated with iproniazid and then iiijected with reserpinc showed extreme “amphetamine-like” stimulation.’ Clinical interest in M A 0 inhibitors per SE as t’herapcuticagents had been awakened. The early experiencte of Zeller and others pointing toward alkyl and aralkyl substituted hydrazines as potent M A 0 inhibitors was present,ed in a recent symposium.8 The National Heart Institut’egroup, making use of iproniazid and some of t’hemany compounds synthesized by Biel aiid his associates, g21a demonstrated that inhibition of M A 0 in the brain does indeed result in increased levels of endogenous amines such as serotonin, norepinephrine, tryptamine and possibly others.”-l* The compounds tabulated in this paper are a selection from over one hundred substituted hydrazines synthesized as part of a program covering a number of years of experience in our laboratory. This program was initiated by the discovery in our laboratories that phenrthylhydrazine was an extremely efficient M A 0 inhibitor, which eventually resulted in a therapeutically succ,essfulantidepressant drug.’j 1000 540
5 28 15 30 >150 5
7.59 7.92 6.71 6.71
7.82 7.87 6.67 6.89
20.55
20.48'"
...
...
125 180 390
10 20 50
CiiHisNzOs Ci1HiaC1Nz0z~ HC1 CsHi4NzO.HzSO4 CsHiiClNz.HzS0~ Ci4HiaNz.HCI
55.65 55.56 67.38 67.38 74.97 74.73 70.56 70.49 22, 25m 22.15 16.51m 16.63 61.83 61.96 63.44 63.37 58.91 58.99 47.32 47.30 40.90 40.80 35.72 35.82 67.55 67.86
C~HirHz.HnS0i CiiHisNzO CisHiiNaO
43.53 43.22 68.72 68.75 70.56 70.68
isopropyl alcohol. e benzene. British Patent 864,108 (1961). 9 3 hr. Med mg./kg. i.p.
CH, e_\tCH,-CH- I
Carbon, Calcd. 57.90 68.72 64.84 61.20 63.44
% Found 57.75 68.77 64.45 61.40 63.59
f
-NX-NY
...
...
11.65 11.81 16.46 16.62 13.37 13.36
...
...
...
...
...
7.26 7.74 7.19 5.78 6.10 4.89 6.89
7.27 ? 76 7.15 5.87 6.21 5.41 7.02
14.42 13.45 12.49 10.04 10.60 11.93 11.26
12.58 13.38 12.35 10.13 10.33 12.02' 11.31
150 212 125 215 460 375 225 175 200
6.50 8.39 6.71
6.83 8.60 7.03
11.28 10.94 14.57 14.35 16.46 16.44
166 345 600
Nicotinoyl. Reported in
... 30 10 10 20 20 25 20 20 10
>50
26
55
Isonicotinoyl. Reported by Biel el a1.10 U. S. Patent 3,000,903 (1961). Chlorine Q
Footnotes same as in Table I.
Hydrogen, % Calcd. Found 8 10 8 34 8 39 8 59 8 16 8 15 7 53 7 51 7 74 7 74
Nitrogen, 70 Calcd. Found 15 01 14 89 14 57 14 86 12 60 12 38 9 52 9 57 13 45 13 70
ReserpineAcute challenge toxicityp te5t9 85 5 30 75 10 180 I000 100 43 in
Method B.-Direct. reaction of a carbonyl cwnipound with excess hydrazinc hydrate, isolation of the resulting hydrazone and catsl)-tic retluctiori (iisirig platinuni oxide and palladium on charcoal) gavr five c*ompoiinils in 40-75% yield. p-Methoxy-a-methylbenzylhydrazine Monooxa1ate.-A solii1,ion of 75.1 g. (0.5 mole) of p-methoxyacetophenoiie in 200 ml. of 957, eth:tnol \\-:is d t l e d dropwise. with stirring, over 1 hr., to a refluxing solution of 100 g. (2.0 moles) of hydrazinc hydrate in 100 ml. of 95y0 ethanol. The mixture was refluscd for 4 hr., cooled. filtered and dried t o yield 64.3 g. ( i 8 i ( > of ) p-inethox~--cu-iiietliyll~eiizylitie~~ehydr:izine, as a yellow solid, m.p. l14-ll~i'. The hydrazone x-as iirixeti u-it>h0.5 g. of PtOs, 2 g. of 5%) Pd on rharroal : ~ n d300 nil. of :ibsolutc, et~lianol.:tnd hydrogrnat,ed, with heating, in a P a r r shaker until tlic ca1ciil:tted :miount of hydrogen !\-vas absorbed (approx. 2 1 hr.). T h r niixture IWS filtered and the filtrate distilled to yield 38.2 g. of p-methoxy-a-riiethylheiizylh-drazinc,, as a colorlrss oil, i>.p. 93-95' (0.09 nini.). The oxalate salt>11i.p. 155- 1 5Ro, \\-as prcq):irrd i i t : i l ) d u t v ethanol and recrystallized from acjueon~ethanol. Method C.-Reaction of an alk>-1carbazste jmethJ-I, ethyl or f-l)utyl) with :i carbonyl compound and catalytic reduction of thc intcrmcdiatc gave 21 subst,ituted alkyl carbazates in 45-947, >-ield. Hydrolysis, with simultaneous dccarboxylation, using cthanolic alkali (Claisen's method) yieldrd five monosiihstituted hydrazines in 50-85% yield. p-Butoxybenzylhydrazine Monooxa1ate.-A mixture of 25 g. (0.14 mole) of p-hntoxybenzaldehyde, 14.6 g . (0.14 molrl of ethyl cnrbazatc and 150 ml. of isopropyl alcohol was reflitxed for 4 hr. The solvent was removed under rnrinim and the residue recrystallized twice from ethyl acetate-pctrolenni ether t o yield 36.4 g. (987,) of et,hyl S-(p-l)utoxyhenzylid~~ni:)carbaznt 1n.p. 111-112O. A mixture of 200 ml. of isopropyl alcohol, 36 g. (0.136 mole) of ethyl :'~-(pbutoxybenzylidene) carbazate m d 0.5 g. of PtO2 was hydrogenated, a-ith heating. in a Parr shaker until the theoretical nmount of hydrogen was n l m r h c d ( 7 hr. initial pressure, 3.5 kg./cm.2). The mixture \\-as filtered, the solvcnt r e n i o \ d under vacuum and the residue recr llized from 50% aqueous niethnnol i o yield 34.7 g. (965;,)of ethyl ~i-(p-~~ntox!-l~enzyl)c:irl~:izatr, as colorless cryst:ils. n1.p. 58-60", .2 mixture of 13.3 g. (0.05 mole) ethyl 3-(p-butoxybenzyl)c~~rbazate, 5 . i g. (0.1 mole) of potassium hydroxide and 150 ml. of absolute ethanol \\-as refluxed for 8 hr. The solvent n-as removed and the residue extracted n-ith tn-o 100-mi. portions of ether. The combined ether extract \\-as filtered and a solution of 9 g . (0.1 mole) of anhydrous oxalic acid i n ether added. The precipit:rte TWS riacrystallized from aqueous methanol to yield 7 . 2 g. (51%) of ,u-butoxyl)enz!-lhydrazine monooxalate, as colorless crystals, n1.p. l i 6 - l i i " . Method D.-Analogous to Method C using an acylhydrazine instead oi an alkyl carbazate: nineteen compounds r e r e prepared by the rediiction of the intrrmediate hydrazones in 60-95% yield. Subsequent hydrolysis gave an additionnl seven substituted hydrazines in 30-65% yield. p-Chloro-a-methylbenzylhydrazineHydrochloride.-A mixture of 2'2.2 g. (0.3 mole) of aretylhydrazine, 46.4 g. (0.3 moles) of /,-chloro:t.cc,tophrri~ii(,nnd 250
March 1962
HYDRAZINES AS MOKOAMIKE OXIDASEINHIBITORS
229
ml. of ethanol was refluxed for 8 hr. and cooled t o yield 63.2 g. (77%) of l-acetyl2-(p-chloro-m-methylbenzylidenejhydrazine, as colorless crystals, m.p. 161161.5'. Recrystallization from isopropyl alcohol raised the m.p. to 169'. A mixture of 39 g. (0.185 mole) of l-acetyl-2-( p-chloro-a-methylbenzy1idene)hydrazine, 250 mg. of PtOz and 275 ml. of methanol was hydrogenated until the calculated amount of hydrogen \vas adsorbed (7 hr.; initial pressure, 3.5 kg./cm.*). The mixture 1%-asfiltered, freed of solvent and the residue recrystallized several times from ethyl acetate-ligroin to yield 37 g. (947,) of l-acetyl-2-(p-chloro-amethylbenzyl)hydrazine, as colorless crystals, m.p. 119-121 '. A solution of 21.2 g. (0.1 mole) of this product in i 5 ml. of 1070 ethanolic potassium hydroxide was refluxed for 8 hr. The solvent v a s removed and the residue extracted with ether. The organic layer was distilled t o yield 6.4 g. (38yo) of p-chloro-amethylbenzylhydrazine, b.p. 90-95' (0.8 mm.). The base (4.0 g.) was dissolved in 250 nil. of dry ether and the solution sahrated with dry hydrogen chloride. The salt, was recrystallized from chloroform-petroleum ether to yield 3.2 g. of colorless c,rystals, n1.p. 146-148". Method E.-Reaction of monoacetylated aralkyl hydrazines with excess acetic anhydride t o yield diacetylated compounds. Three compounds prepared by this method are reported in Table I in 40-55% yields. 1,2-Diacetyl-2-p-n-butoxybenzylhydrazine.-Amixture of 17 g. (0.072 mole) of I-acetyl-2-p-n-butosybenzylhydrazine, 50 ml. of acetic anhydride and 1 drop of concd. sulfuric acid was heated for 0.5 hr. 011 a steam bath. After standing overnight, the acetic anhydride was removed under vacuum, the residue washed with water and recrystallized several times from ethyl acetate-petroleum ether t o yield 8.4 g. (41.5%) of colorless, fluffy needles, m.p. 89-91'. Method F.-Analogous to RIethod E, using an alkyl chloroformate in place of acetic anhydride with yields of i5-80%. l-Carbethoxy-2-carbomethoxy-l-(a-methylbenzyl)hydrazine.-A mixture of 19.4 g. (0.1 mole) of methyl 3-(~-methylbenzyl)carbazate,11.9 g. (0.11 mole) of ethyl chloroformate, 12.6 g. (0.15 mole) of sodium bicarbonat,e and 200 ml. of absolute et,hanolwas refluxed for 1 hr. and filtered hot. Removal of the solvent and distillation of the residue yielded 21.3 g. (S070) of colorless, viscous oil, ~ b.p. 160-162" (0.7 nixn.); n z 2 1.5091. Method G.-Reaction of an aralkyl hydrazine with a cyclic carbonate (ie., ethylene carbona,te) to yield an a-hydroxyalkyl carbazate. Subsequent treatment with thionyl chloride yields the a-chloroalkyl carbazate. This is essent,ially the method described by Delaby et al." p-Chloroethyl 3-Phenethylcarbazate Hydrochloride.-A mixture of 44 g. (0.5 mole) of ethylene carbonate and 68 g. (0.5 mole) of phenethylhydrazine was heated on a steam bath for 1 hr. The reaction mixture was extracted with 500 ml. of boiling benzene. Cooling the benzene layer yielded 85 g. (64%) of phydroxyethyl 3-phenethylcarbazate as colorless crystals, m.p. 90'. Recrystallization from benzene and drying for analysis raised the m.p. to 98-99'. A mixture of 58 g. (0.26 mole) of p-hydrosyethyl 3-phenethylcarbazateJ 40 g. (0.83 mole) of thionyl chloride and 1000 ml. of benzene was allowed to stand for (21)
R . Ddaby, R . Ilaniiens, and N . L Capmau, Compt. rend., 246, 3353 (1958).
“-1 hr.
The Iteiizene a n d CSCYW tliionyl chloride \vue reiiiovctl mcl I he residue ( 3 3 g.) \vas recrystallized sctveral t,iiiies froill ethyl acctate-pet,rolcuin ether to yield 21 g . (29%) of p-c~lilorocthyl :~-r)lienethylc:trbaz:ttc liydrorhloritir, m.p. 163.5164’. Structure-Activity Relationships.-The compounds reported in this paper were put through our general screening program, with results that mere interesting and in some cases surprising. In general, comparing monosubstituted hydrazines with their acyl derivatives, the monosubstituted hydrazines were found to be the most active and the most toxic. The carbazntes were slightly less act,ive and less toxic. The acetyl derivatives were the least, active and least t,oxic. However, acute toxicity and act,ivity were not, directly related from one homologous series to the next,. For example, p-phenoxy-a-ineth?-lbenzylhydraaine is one of the most active and least toxic of the compounds. The relative activity of the acetylated and carboalkoxylated aralkyl hydrazines apparently is dependent upon the relative rates of hydrolysis of these blocking groups, yielding the free aralkyl hydrazines. Observations in the course of preparing the free hydrazines from the acylated compounds suggest that the in vivo activity of the coinpound is proportional to the rat,e of c:heniical hydrolysis of the blocking group. In addition, studies with ethyl 3-( a-niethylbenzy1)carbazate show that, although it is among the niore potent inhibitors i n vivo (reserpine challenge and elevation of brain actrotonin), it is ouly :L weak inhibitor of M A 0 in vitro. Compounds containing bulky pula substituents (such its butoxy, phenyl, phenoxy, etc.) appear to he the most potent and least toxic on the basis of this preliminary work.
